Write the Word or Phrase That Best Completes Each Statement $70 ^ { \circ }$

Write the word or phrase that best completes each statement or answers the question.
-The temperature (in degrees Fahrenheit) of a dead body that has been cooling in a room set at $70 ^ { \circ }$ is measured as $88 ^ { \circ }$ . One hour later, the body temperature is $87.5 ^ { \circ }$ . How long (to the nearest hour) before the first measurement was the time of death, assuming that the body temperature of the deceased at the time of death was $98.6 ^ { \circ }$ . Assume the cooling follows Newton's Law of Cooling:
$$\mathrm { U } = \mathrm { T } + \left( \mathrm { U } _ { \mathrm { O } } - \mathrm { T } \right) \mathrm { e } ^ { \mathrm { kt } }$$